HSC Survey Results

Scots Bay Survey # 11 Results from 23/09/2024

Survey Details

4 commercial purse seiners conducted this fishing survey on 23/09/2024 starting at 20:00:00, which was 3.45 hours after hide tide.

All vessels ran two transects each in the Main Survey Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Janice II.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Tides Tables

Tide Schedule for Margaretsville NS, Station #315m Source: www.waterlevels.gc.ca

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for Scots Bay using standardized parallel transects is 8,735mt, and with turnover applied 7,098mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
BP T01 2024-09-23 19:00:20 2024-09-23 21:37:36 -65.235 45.092 -64.837 45.226 SB 34.70 7.15
BP T02 2024-09-23 21:56:36 2024-09-23 23:03:46 -64.901 45.265 -65.163 45.187 SB 22.49 10.85
C1 T01 2024-09-23 19:09:24 2024-09-23 22:23:10 -65.245 45.071 -64.742 45.237 SB 45.85 7.67
C1 T02 2024-09-23 22:48:49 2024-09-24 01:16:46 -64.809 45.295 -65.220 45.150 SB 37.29 8.17
LJ T01 2024-09-23 19:23:26 2024-09-23 22:49:57 -65.238 45.051 -64.706 45.228 SB 46.47 7.29
LJ T02 2024-09-23 23:19:32 2024-09-24 02:01:11 -64.783 45.284 -65.235 45.129 SB 39.65 7.95
MS T01 2024-09-23 19:16:24 2024-09-23 23:05:53 -65.230 45.037 -64.682 45.216 SB 50.29 7.10
MS T02 2024-09-23 23:40:41 2024-09-24 02:34:04 -64.765 45.272 -65.238 45.108 SB 42.85 8.01

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
BP T01 -35.5 -51.220 0.027
MS T01 -35.5 -52.147 0.022
MS T02 -35.5 -53.383 0.016
LJ T01 -35.5 -54.358 0.013
C1 T01 -35.5 -55.210 0.011
LJ T02 -35.5 -55.894 0.009
BP T02 -35.5 -57.713 0.006
C1 T02 -35.5 -59.813 0.004
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
Main Box -35.5 628 -54.0666 0.0134 8,735 100 100 1,739.93 19.92

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by BP, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by BP, at the following location:

Annual Summaries

This table does not include the biomass from adhoc surveys.

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
Scots Bay 1 2024-05-05 78,662 78,662 2023-05-22 40,856 40,856 47,629 47,629
Scots Bay 2 2024-05-20 29,842 17,255 2023-06-06 113,767 108,783 98,582 92,772
Scots Bay 3 2024-06-02 93,804 89,523 2023-06-18 34,279 15,158 29,417 12,720
Scots Bay 4 2024-06-16 33,347 22,278 2023-07-02 11,745 5,113 9,330 3,622
Scots Bay 5 2024-07-01 7,252 3,123 2023-07-16 19,283 17,575 17,387 16,022
Scots Bay 6 2024-07-15 4,539 3,560 2023-07-30 4,550 1,904 3,474 1,093
Scots Bay 7 2024-07-29 32,655 32,016 2023-08-13 4,299 3,616 2,777 2,247
Scots Bay 8 2024-08-11 15,213 10,296 2023-08-27 2,897 2,300 1,612 1,224
Scots Bay 9 2024-08-25 9,206 6,810 2023-09-10 3,054 2,916 3,219 0
Scots Bay 10 2024-09-08 13,418 12,121 2023-09-24 3,420 2,997 2,318 0
Scots Bay 11 2024-09-23 8,735 7,098 2023-10-09 3,388 2,971 2,521 0
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 Scots Bay 241,538 204,189 218,266 177,329
2024 Scots Bay 326,673 282,742 NA NA

Tagging, Plankton, and CTD Data

Summary map

Vessel Tags

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Janice II Lady Janice II
Set Number SB2023-19 SB2024-20
Ground SB SB
Date 23/09/2024 23/09/2024
Wind Direction (km/h) NE NE
Swell (m) 0.5 0.5
Air Temp (c) 14 14
Tow Details
Tow Start 18:26:00 18:42:00
Tow End 18:36:00 18:52:00
Start Lat 45.05033 45.05717
End Lat 45.05367 45.05817
Start Lon -65.22167 -65.21417
End Lon -65.21883 -65.20883
Avg Tow Depth (m) 2.194026 1.893785
Speed 1.4 1.5
Heading 29 71
Tide Direction against against
Other Data Collection
Flow Start 862772 894742
Flow End 894742 931393
No. Revolutions 31970 36651
Distance (m) 859.1298 984.9223
Volume 2698.956 3094.133
Secchi Disappear (m) 9 9
Secchi Reappear (m) 8 8

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is SB2023-19, which was against the tide and had an average depth of 2.1940261m. The second tow is SB2024-20, which was against the tide and had an average depth of 1.8937846m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 Scots Bay surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for Scots Bay.

Vessel Performance

Speed

Average vessel speed was 8.02. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

The speed for each transect are rudimentary and are calculated based on distance. If a significant amount of distance is cut, the speed will appear slower.

Distance

No significant distance was cut from the planned lines; vessels covered the planned area well.